Microcapsules composed of a shell prepared by a sol-gel process has been described in various publications:
U.S. Pat. Nos. 6,303,149, 6,238,650, 6,468,509, 6,436,375, US2005037087, US2002064541, and International publication Nos. WO 00/09652, WO00/72806, WO 01/80823, WO 03/03497, WO 03/039510, WO00/71084, WO05/009604, and WO04/81222, disclose sol-gel microcapsules and methods for their preparation. EP 0 934 773 and U.S. Pat. No. 6,337,089 teach microcapsules containing core material and a capsule wall made of organopolysiloxane, and their production. EP 0 941 761 and U.S. Pat. No. 6,251,313 also teach the preparation of microcapsules having shell walls of organopolysiloxane.
U.S. Pat. No. 4,931,362 describes a method of forming microcapsules or micromatrix bodies having an interior water-immiscible liquid phase containing an active, water-immiscible ingredient. As a capsule-forming or matrix-forming monomer, an organosilicon compound is used.
Microcapsules prepared by a sol-gel process are also disclosed in GB2416524, U.S. Pat. No. 6,855,335, WO03/066209.
Such microcapsules have use in various applications where chemical contact between the active ingredient and the immediate environment should be minimized, e.g. colorants for cosmetics, food colors, sunscreen compositions or in other applications where delivery of the active ingredient is of benefit (e.g. topical delivery onto the skin). However, for certain applications such as parenteral administration, oral administration, textile industry, it will be highly advantageous to have nanocapsules, particularly having a narrow size distribution, which are inert, simplified in production, can be easily incorporated in various carriers, which are capable of isolating and/or releasing the active ingredient therefrom, depending on the intended use, and yet which are physically stable during storage (e.g. do not form agglomerates, preferably do not form agglomerates even in compositions substantially free of surfactants) thereby providing long term use of the formulation.